Light Buffer from BaseColor and SceneColor

Hey there. I know there is no direct way to get how lit is a pixel in a Post Proccess material with a SceneTexture node. Anyway, I figured out there must be a formula that takes SceneColor (or PostProccessInput0) and BaseColor and returns how much light is the pixel receiveing. Thing is, I’ve tried both dividing and substracting them and I can’t get a decent result. Any ideas?

Hi Mago, did you ever figure out such an equation? I would imagine it might be impossible, say for example that a zebra is pitch black on its dark stripes, surely the lighting information would be completely gone without a trace in such an example? (i.e. since the lighting was multiplied by 0, i.e. the zebras dark spot)